The long range objective of this study is to examine the effects of endothelial cell membrane lipid modification on the fibrinolytic activity of the vascular endothelium and extracellular matrix (ECM) and their potential modulation by two potent endothelial cell mitogens with angiogenic properties, basic fibroblast growth factor (bFGF) and transforming growth factor-beta (TGF-beta). Intricate relationships exist among endothelial cells, fibrinolytic molecules (tissue plasminogen activator (t-PA)) and its inhibitor plasminogen activator inhibitor-1 (PAI- 1), and angiogenic mitogens that can regulate the fibrinolytic activity of the vasculature. Cellular cholesterol and saturated fatty acid enrichment as well as oxidized low density lipoprotein (LDL) have been demonstrated to induce dysfunction of endothelium in the pathogenesis of atherosclerosis. This project will test the hypothesis that endothelial cell membrane lipid modification will modulate fibrinolytic responses to angiogenic mitogens and the net fibrinolytic properties of the endothelium and its ECM. The specific aims can be summarized as follows: 1. To investigate the effects of lipid modification of the endothelium on t-PA and PAI-1 activity, antigen levels, and mRNA levels; 2. To examine the effects of endothelial cell lipid modification on modulation of t-PA and PAI-1 protein secretion and regulation by bFGF and TGF-beta; 3. To characterize the effects of endothelial cell lipid modification on PAI-1 content of the ECM and its modulation by bFGF and TGF-beta; and 4. To study the effects of endothelial cell lipid modification on endothelial t-PA receptor synthesis and membrane availability and their potential modulation by bFGF and TGF-beta. Consequently, these studies should contribute to our knowledge of the regulation of the endothelial fibrinolytic system by lipid modification and mitogens, thereby elucidating the role for these important factors in the pathogenesis of atherosclerosis and thrombosis.